Steam boiler



Nav. l, 1927.

1,647,638 E. KlDwELL.

STEAM BOILER Filed March 9, 1925 2 Sheets-Sheet 1 Patented Nov. 1, 1927.

UNITED STATES PATENT OFFICE.

EDGAR KIDWELL. 0F MILWAUKEE, WISCONSIN, ASSIGNOR T0 KIDWELL BOILER COM- PANY, 0F MILWAUKEE,

WISCONSIN, A CORPORATION OF WISCONSIN.

STEAM BOILER.

Application filed 'March 9, 1923. Serial No. 623,832.

This invention relates to steam boilers that are equipped with furnaces for the utilization of pulverized coal as fuel. In such constructions. when the flame is directed upwardly to or across the furnace, the ash content of the coal, which becomes fused during` eomlnistion, is projected upon the boiler tubes and adheresvthereto, forniing a covering of dense glassy slag, and when the flame is directed downwardly in the furnace, such slag is similarly' formed in the bottom of the furnace and thus accumulates therein. The removal of the covering or accumulation of slag is in either case a tedious and expensive performance. To overcome the objection just indicated to the use of pulverized fuel in steam boilers, a grate built up of water-tubes and constituting a so-called water-Screen, has been arranged in the bottom of the combustion chamber and connected with the eirculating system of the boiler in such a manner that the grate tubes tend to absorb the radiant heat from the fire and thus cool the bottom of the chamber and the gases therein to an extent sufficient to prevent the formation or accumulation of liquid slag, that is to say, the slag falls to the bottom of the chamber in theA form of powder or small lumps so reduced in temperature that it does not stick together, but can be raked out like ashes.

As heretofore constructed the up-comer connection of the water-screen by which it delivered the effluent to the boiler above, extended through the forward heat or gas passes and was thus subjected to both the sensible and radiantheat from the flame in the combustion chamber, with consequent liability to burn and become ruptured in a short period of time. Therefore my invention has for its object to provide in a steam boiler, particularly of the series tube-and drum type, a water-screen whereof the inlet and outlet connections are directly. coupled to portions of the boiler circulating system located in the region of the rear pass or passes of the apparatus, so that the water-filled screen tubes only are exposed tothe full furnace temperature and direct radiant heat from the flame.

Another object of the invention is to proj vide a construction whereby the supply of water to the water-screen is taken from the boiler in such a manner as to avoid the entry of water-mud into the screen tubes.

A yfurther object of thel invention is to provide a construction wherein the steam evolved in the water-screen is efl'ectually f delivered to the upper portion of the boiler in a manner to avoid any liability of overi loading the up-comer passages in the boiler,

which are already fully taxed with the steam generated in the type equipped with a ytubular water-screen embodying the principle of my invention.

Fig. 2 is a transverse vertical section through the rear tube bank of the boiler and the associated tubes between the rear :team-and-water drum and the tubular water-screen. as on the line 2-2 of Fig. 1.

Fig. 3 is a similar section immediately above the tubular watenscreen, as on the line 3 3 offFig. l.

Fig. 4 is a sectional detail, enlarged, of the mud drum and adjuncts.

Fig. 5 is a vertical section of the lower portion of a boiler structure equipped with' a modified form of water-screen connection. lVhile my invention is herein illustrated as efficiently applied to a steam boiler of the series tube-and-druiri type wherein transverse drums and associated banks of water'tubes, together with suitable baflling are employed, it is to be understood that the invention is not limited to a boiler of that particular type, nor to the specific Water-screen and connections herein described, since other forms of boilers may be used and since the construction of the screen and its connections may be modified within the principle of the invention and the scope of the appended claims.

Referring to the drawings, 10 designates the boiler setting; ll the combustion chamber therein for pulverized fuel, and l2 the bridge wall spaced from the rear wall of the setting. 13 designates a series of burners suitably arranged to direct the flame downwardly into the forward part of the leads into the rear drum 17.

combustion chamber, and 14 designates the outlet or breeching to the smokestack at the rear of the setting.

15 designates aniud drum located at the I. rear of the bridge wall of the combustion chamber; 16 a water drum located above thel forward portion of the said chamber and below the normal water-level, and 17, 18 two steam-and-water drums arranged above the drums 15, 16 respectively. The drums 17, 18 are located partly above and partly below the normal water-level, thus providing in each a lower water .space and an upper steam space. 'lhe feed-water pipe 10 The drums 15, 16 and 17 are connected iu succeeding order by banks ot' tubos 20, 21. 22 respectively, thus providing a continuous circulation path for the water: and battles 23 are suitably disposed in relation to such banks in order to direct the hot gases and other products of combustion through succeeding passes from the front to the rear of the apparatus, whereby a continuous circulation of the water through the drums and tubes is effected.

.The steam space of the rear upper drum 17 is connected with the similar space of the front upper drum 18 by means of a series of tubes 24 arranged within the path of. the

hot gases from the combustion chamber, whereby the steam as rapidly as it is liberated from the water in the drum 17 flows into the steam-space of the front upper drum 18, such steam, during its passage through the tubes 24,' being dried or super-heated. The drum 18 is provided with a discharge portion 25 through which the dry or superheated steam as rapidly as it is produced is taken off for service. The discharge portion 25 is also connected to the steam end of the water gauge.

The front and rear steam-and-water drums are connectetd by oppositely inclined tubes 26, 27 which, in conjunction with the front steam-and-water drum, constitute a supplemental path through which a portion of the main body of water is diverted from the main path of circulation in such a `manner that there is effected and maintained between the two drums 17, 18 a continuous water circulation which ensures a steady level of water within the front steam-and-water drum, as set out in my. Letters Patent of the United States /No. 1,442,433 dated J anuary 16, 1923.

No claim is made herein to the typical apparatus thus far described, excepting as certain elements thereof cooperate wit-h the water-screen construction now to be explained.

The water-screen, which extends throughout the width and length of the lower part of the furnace chamber, comprises, in its preferred construction, two series of tubes 28,

29 arranged one above the other` with the tubes of one alternating with or in staggered relation to those of the other series. The tubes 28, 29 extend longitudinally of the fur- 'nace chamber and project through and somewhat beyond the front and rear walls of the latter; the lower row being inclined upwardly from the back to the front and the upper row being reversely inclined, that is, upwardly from the front to the back. The forward ends of the two series of tubes are connected by a transverse header 30 which establishes communication between the two series. The rearward ends of the lower series of tubes are connected by means of a transverse header 31 which, in turn, is connected with the mud drum by means of a series of tubes 32, constituting downcomers. These tubes 32 are tapped into the lower rearward side of the mud drum and are provided lwith upwardly and forwardly inclined guard tubes 33 of sulicient length to extend across the path of discharge of the water from the tube bank 22 into the mud drum. In the present instance the guard tubes are tted to a pad 34 that is riveted to the Wall of the mud drum, such tubes being clamped to the pad by suitable set-screws 35. The rearward ends of the upper row of tubes 29 are connected by 4means of a transverse header 36, which, in turn, is connected with the rearward steam-and-water drum 17 by means of a series of tubes 37, constituting upcomers, that are substituted for a corresponding number of tubes of the rearward bank. The two series of down-comer and 11p-comer tubes correspond in number with each other, the latter tubes bein interspersed withthe back row tubes of t e rear tube bank and having their upper ends curved similarly to the adjacent tubes of the bank to permit their efficient entry into and connection with the drum 17, as near to the water surface as possible.

From the foregoing described construction it will be seen that in the operation of the boiler, water flows from the upper part of the mud down into and through the screen tubes, and returns thence in the form of steam through the 11p-comers to the steamdisengaging drum 17 of the boiler; the guard tubes 33 avoiding the passage of mud into the down-comer tubes, either from the accumulations in the drum or directly from the water 'flowing into the drum from the rear. tube bank.

Since the tubes 32 are located rearwardly of the combustion chamber and the tubes 37 are located in the rear tube bank, the said tubes are not exposed to the direct furnace heat, and therefore liability' of their burning out is obviated, and since the tubes 37 are substituted for a corresponding number of the tubes of the rear bank and discharge into the drum 17 there is no liability of the steam that is generated in the screen tubes overloading the 11p-comer passages of the boiler. Furthermore, should the boiler water happen to fall to an extremely low level the water screen nevertheless will be supplied with water through its connection with the. mud drum, and hence all danger of accidentally burning out the screen tubes, on account ot' the evaporation of the water therein. will be avoided.

IVhile I have shown and described the upcomer tubes 37 as ranging with and replacing certain back row tubes ot the tube bank 22, it is to be understood that such up-comer tubes may range with and replace any tubes in said bank 22, without departure from my invent-ion.

In Fig. 5 is shown a modified construction wherein/the water is supplied to the screen tubes from the interior of rthe steam-andwater drum 17 instead of from the mud drum. In this construction the header 31 for the lower vseries of screen tubes is connected with the water space of the rearward steam-andwater drum 17 by means of a series of down-comer tubes 32 that are substituted for a corresponding number of the back row of tubes of the rearward bank. Hence water is supplied to the screen tubes from the rear steam-and-water drum by means of the down-comers.

I claim- 1. In a boiler having a main water-circulat-ing path and a lower combustion chamber, said path extending rearwardly of the chamber, a tubular water screen arranged within said chamber, and water inlet and outlet connections for said screen, said connections each comprising tubes directly communicating with said water-circulating path at points therein rearwardly of the combustion chamber, said tubes being disposed within the boiler setting and entirely outside the combustion chamber.

2. In a boiler having a main water-circulating path and a lower combustion chamber, said path extending rearwardly of the chamber, a tubular water screen arranged within said chamber, and water inlet and outlet connections for said screen, said connections each comprising tubes directly communicatin with said water-circulating path at points therein rearwardly 'of the combustion chamber, said tubes being disposed within the boiler settin and entirely outside the combustion cham er, the outlet tube connections leading to an u per part of said path adjacent the level of t e boilerI water. I

3. In a boiler havin a main water-circulating path and a com ustion chamber, said path including an upper rearward chamber wherein the steam is disengaged from the water, a tubular water-screen in said combustion chamber, and down-comer and` upcomertubes connecting the said screen with from the front to the rear of the structure,

and a combustion chamber opening into the front pass. a. tubular water-screen arranged within said chamber, and water inlet and outlet connections for said screen, said connections each comprising tubes located within the boiler setting entirely outside the combustion chamber and directly communieating with the rearward part of the watercirculating pathof the boiler. a portion of the outlet tube connections being located within a heat pass and leading to an upper part of said path adjacent the level of the boiler water.

5. In a boiler of the series tube-and-drum type, including a rearward upper steam-andwater drum, a rear lower mud drum, and a bank of tubes connecting said drums, and including also successive heat passes leading from the front to the rear of the structure, and a combustion chamber forward of said mud drum and opening into the front pass, a tubular water-screen'arranged within said chamber, and inlet and outlet connections for said screen, said connections each comprising tubes directly communicating with the rearward part of the water-circulating path, the upper portion of the outlet tube connection leading to the said steam-and-water drum andrbeing located entirely outside the combustion chamber and within a heat pass.

6. In a boiler lof the series tube-andedrum type, including a rearward upper steam-andwater drum, a rear lower mud drum, and a bank of tubes connecting said drums, and including also successive heat passes leading from the front to the rear of the structure, and a combustion chamber forward of said mud drum and opening into the front pass, a tubular water-screen arranged within said chamber, and inlet and outlet connections for said screen, said connections comprisingv tubes directly communicating with the rearward part of the water-circulating path, the outlet tubes being substituted for a corresponding number of tubes of the said bank located entirely outside of the combustion chamber the upper portion thereof being within a heat pass and leading to the said steam-and-water drum.

7. In a boiler of the series tube-and-drum type, including a rearward upper steam-andwater drum, a rear lower mud drum, and a bank of tubes connectin including also successive Iieat passes leading from the yfront to the rear of the structure, and a combustionchamber forward of said kmud drum and opening into the front pass,

said drums, and

a tubular water-screen arranged within said chamber, and inlet and outlet connections for said screen, said connections each cornprising tubes directly communicating with the rearward part of the waterrirculating path, the outlet tube connections being subl stituted for a corresponding number of the back row of tubes of the said bank located entirely outside the combustion chamber and partially Within a heat pass and leading to the said steam-and-u'z-.ter drum.

8. In a boiler oi" the series tube-and-druin type, including a rearward upper steam-andwater drum, a rear lower mud drum, and a bank of tubes connecting said drums, and including also successive heat passes leading from the front to the rear of the structure, and a combustion chamber forward of said mud drum and opening into the front pass, a tubular water-screen arranged within said chamber, and inlet and outlet connections for said screen`r the inlet connections comprising tubes communicating with the mud drum, and the outlet connection comprising tubes communicating with the steam-andwater drum, said latter tubes being substituted for a corresponding number of tubes of the said bank located entirely outside the combustion chamber and partially within a heat pass and opening into the said steam' and-water drum. v

9. In a boiler of the series tube-and-drum type, including a rearward upper steam-andwater drum, a rear lower mud drum, and a bank of tubes connecting said drums, and including also successive heat passes leading from the front to the rear of the'structure, and a combustion chamber forward of said mud drum and opening into the front pass,

a tubular water-screen arranged within said chamber, and inlet and outlet connections for said screen, the inlet connection comprising tubes communicating with the mud drum and having upwardly and forwardly inclined guard members entering the shell of said drum at points outside the combustion chamber and extending across the path of discharge of the water from the said tube banks int-o the drum and the outlet connection comprising tubes communicating with the steam-and-water d runi, said latter tubes being substituted for certain tubes of the said bank and opening into the said steamand-water drum.

l0. In a boiler having a transverse steamaud-water drum, a lower mud drum parallel thereto, a bank of water-tubes connecting said drums, and a combustion chamber having a rearward bridge wall locatedy forwardly of said tubes, a water-screen arranged within said chamber and comprising two series of tubes in spaced relation to each other and extending longitudinally of the chamber, a header connecting both series of screen tubes forwardly of the chamber, headers connecting the respective tubes of each series rearwardly of the chamber, and down-comer and up-comer tubes connecting the latter headers with the mud drum and steam-and-water drum respectively, said down-comer and up-comer tubes being disposed within the boiler setting and entirely outside the combustion chamber.

Signed at Milwaukee, in the county of Milwaukee and State of Wisconsin, this 6th day of March A. D. 1923.

EDGAR KIDWELL. 

